This invention relates to valves and more particularly to valves for controlling the flow of gases in large ducts, flues, chimneys and the like.
An object of my invention is to provide a valve of the character designated which comprises a plurality of cooperating closure members which, when the valve is closed cooperate to form a closed space extending across the duct, thereby not only controlling the flow of gas in the duct, but also affording a chamber into which gas under pressure greater than that of the gas being controlled may be introduced, thus to assure zero leakage of the controlled gas past or around the closure members.
Another object is to provide a valve in which the end movable members thereof, when open, automatically seal or close the opening through which external air is introduced into the closures when the latter are closed, thereby eliminating the need for a separate valve for controlling such flow into the chambers formed by the members.
Another object is to provide a valve for controlling the flow of fluids such as gases in large ducts and the like which, when in open position, offers minimum resistance to the flow in the duct.
Other objects of my invention are to provide a valve in which some of the closure members are essentially Z-shaped in cross section, the legs of the Z-shaped sections carrying flexible seal members, the connecting legs of the Z-shapes having holes therein, together with other closure members, the parts being so arranged that when closed the entire assembly forms a hollow, sealing closure for the duct, together with means to introduce fluid under pressure into the hollow sealing closure at a pressure greater than that of the controlled fluid.
Another object is to provide a valve of the character designated which is self-cleaning in that high velocity pressurized air is blown over the sealing surfaces automatically during closing of the valve, cleaning the sealing surfaces, resulting in better sealing of the valve.